Thoughts on Sorotec alu-line machine

[NordicCnc]

I have taken some inspiration from the gantry design in your machine. What I've done differently is:

• It is far from done and many details are still missing. One gantry side is still missing completely.
  
• Y-axis linear rails are side mounted to the 160x80 item profile. This allows a larger work area and the ball screws can be mounted to the same piece of aluminium plate, with a little bit of machining.
  
• Gantry side plate is on the inside and an 80x80 item profile is mounted on the outside of the plate. The 80x80 item profile is mounted to the X-axis 200x80 item profile with a back plate and a bottom plate.
  
• The X-axis ball screw and linear rails are all on the front side. With some machining on of the aluminium plates, I am able to squeeze everything in the with custom made ball screw nut brackets.
  
• The Z-axis is made stiffer with side plates bolted onto the same plate to which the linear rails and ball screw is bolted.
  

Please let me know what you think! Are there any significant improvements I could do to make it better?

[JAZZCNC]

The main issue I see is the Z-axis and the unnecessary weight of it.!

You don't need or want the motor and ball-screw on the front plate because you are just moving around dead weight which will affect the z-axis negatively due to high inertia. Those 180W servos won't handle that weight, especially if your planning on using a large spindle or ATC spindle. You will also need a brake to stop it dropping when unpowered.

Ideally, you want a light but strong front plate with no excess baggage to affect inertia. The ball-screw could easily go on the rear plate and be shorter, the motor could mount to plate coming off slightly longer rear plate. This longer rear plate will also allow more spacing of the bearings which will stiffen things up a little.

The other thing I don't like is the ball-screw on the front. If it was me I'd mount it at the rear out fo the way of chips etc and have the ball-nut mount to the plate which the Z-axis motor mounts onto. Don't worry about the ball-nut not being in the so-called theoretical ideal central sweet spot of the front plate because in real-world the difference isn't noticeable. However, weight in the wrong place very much does affect the machine.

[NordicCnc]

The main issue I see is the Z-axis and the unnecessary weight of it.!

You don't need or want the motor and ball-screw on the front plate because you are just moving around dead weight which will affect the z-axis negatively due to high inertia. Those 180W servos won't handle that weight, especially if your planning on using a large spindle or ATC spindle. You will also need a brake to stop it dropping when unpowered.

Ideally, you want a light but strong front plate with no excess baggage to affect inertia. The ball-screw could easily go on the rear plate and be shorter, the motor could mount to plate coming off slightly longer rear plate. This longer rear plate will also allow more spacing of the bearings which will stiffen things up a little.

The other thing I don't like is the ball-screw on the front. If it was me I'd mount it at the rear out fo the way of chips etc and have the ball-nut mount to the plate which the Z-axis motor mounts onto. Don't worry about the ball-nut not being in the so-called theoretical ideal central sweet spot of the front plate because in real-world the difference isn't noticeable. However, weight in the wrong place very much does affect the machine.

Thanks man, Ill revise my design and start a build log to collect more feedback!

Do you still recommend that the linear rails stay on the Z-axis front plate? It would be significantly less weight to move if they are on the Z-axis rear plate, but not as stiff of course. Stiffness could however be increased with some aluminium strips.

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[JAZZCNC]

Do you still recommend that the linear rails stay on the Z-axis front plate? It would be significantly less weight to move if they are on the Z-axis rear plate, but not as stiff of course. Stiffness could, however, be increased with some aluminum strips.

If I'm honest I don't find there's a lot of difference between them. I used to build all my machines using rails on the front plate and yes it is slightly stronger but it does have some drawbacks. The weight is one but the other is tool height or should say gantry clearance because of the tool length sticking down below the gantry.

With the rails on rear plate, you can raise the tool above the bottom of the gantry allowing for longer tools or a lower gantry clearance if you don't need the height for the material.
The machine in the video as the rails on the backplate.

[NordicCnc]

If I'm honest I don't find there's a lot of difference between them. I used to build all my machines using rails on the front plate and yes it is slightly stronger but it does have some drawbacks. The weight is one but the other is tool height or should say gantry clearance because of the tool length sticking down below the gantry.

With the rails on rear plate, you can raise the tool above the bottom of the gantry allowing for longer tools or a lower gantry clearance if you don't need the height for the material.
The machine in the video as the rails on the backplate.

Thats a good point with the tool length. Although I am struggling to think of any kind of tool with that length other than some extremely long drill. Also the distance between the tool and the rear plate in the y-axis and x-axis direction limits the work area in that case. And as you said, it comes down to if the material requires a larger gantry clearance.

I really think the extra stiffness with the rails on the front plate may be worth it. I also think that I will need the gantry clearance for material at some point and less long tools.

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[JAZZCNC]

Thats a good point with the tool length. Although I am struggling to think of any kind of tool with that length other than some extremely long drill.

I've built a lot of machines that are used for mold or model making for wind tunnels etc in blocks of high-density foam or modeling clay and they use long tapered endmills that are 100mm or longer so, in this case, the rails on front plate design won't work as it cannot lift the tool clear of a tall block of foam.

These machines are designed at the outset for a specific purpose to do a specific job or jobs using similar materials within a known size range. The problem is that if you want an all-round machine to cut all materials and with larger material size range then there will always have to be some kind of compromise unless you take a radical approach and design outside the box so to speak.!

If you are using conventional build designs, which you are, then the machine will be compromised in some area it's as simple as that and there's no getting around it.!

If you want to explore outside the box then you can have a machine that will cut the complete range of materials without any compromises on cut quality and material size range other than the cutting area will be a little less in long-axis direction for the same size machine. I can be done but it's a completely different design that will cost more money.?

[NordicCnc]

I've built a lot of machines that are used for mold or model making for wind tunnels etc in blocks of high-density foam or modeling clay and they use long tapered endmills that are 100mm or longer so, in this case, the rails on front plate design won't work as it cannot lift the tool clear of a tall block of foam.

These machines are designed at the outset for a specific purpose to do a specific job or jobs using similar materials within a known size range. The problem is that if you want an all-round machine to cut all materials and with larger material size range then there will always have to be some kind of compromise unless you take a radical approach and design outside the box so to speak.!

If you are using conventional build designs, which you are, then the machine will be compromised in some area it's as simple as that and there's no getting around it.!

If you want to explore outside the box then you can have a machine that will cut the complete range of materials without any compromises on cut quality and material size range other than the cutting area will be a little less in long-axis direction for the same size machine. I can be done but it's a completely different design that will cost more money.?

Regarding the budget I have planned to stay within 6000-7000€. I have already bougth the 180W JMC servos and power supplys. What is left of the budget is then 5150-6150€.

I am definately going for an all round build. Requirements are:

- 180W JMC servos.
- Work area of approximately 1000x1000x200mm. More is appreciated. Work area is needed for making furniture occasionally, custom signs etc.
- The machine needs to be moveable later when I build my own garage. I am currently using my fathers. This is why I am opting for aluminium profiles instead of a welded frame.
- Machine needs to be able to handle aluminium with good finish. The idea is that I could also potentionally use it to build a VMC later that would be for milling aluminium and steel.
- ATC spindle would be nice but it is not a requirement if it means that my budget will not be enough in other more important areas. I am looking at Jianken ATC spindles but I am open for suggestions!

Have I shoot myself in the foot with the JMC servos?

From where should I buy linear rails, bearings and ball screws? I have heard good things about BST automation.


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